A MICS/MEDS based system includes at least a medical controller, also known as hub, and a medical implant, also known as node, operating in the MICS band 402-405 MHz or the MEDS band 401-402 MHz and 405-406 MHz, with a channel bandwidth of 300 kHz. The medical implant is located inside the body of a living organism and the medical controller is, in most cases, externally located. The power consumption by the transceiver forms a significant portion of the overall power consumption in the medical implant. Hence, it is desired to maximize efficiency of the medical implant transceiver to increase lifetime of the medical implant.
The power of the medical implant transceiver is utilized for performing various functions. In one example, the power consumption in the medical implant transceiver is dominated by an unconnected state of the medical implant transceiver. In the unconnected state, the medical implant transceiver wakes up periodically, such as every few seconds, and searches for a signal for connection with an external controller. In an connected state, the medical implant transceiver follows a procedure similar to that for the unconnected state, and wakes up periodically, which may be every few seconds, and searches for the external controller with which it has connected. In one example, the medical implant transceiver in a connected state follows the procedure because the medical implant needs to detect another medical controller transceiver. For example, if the medical implant is initially connected with a medical controller at home, but the living organism including the medical implant transceiver travels to a doctor's office, then the medical implant needs to detect and connect with the medical controller at the doctor's office. Hence the medical implant transceiver wakes up periodically, even when the medical implant transceiver is already connected with a medical controller, to detect other medical controllers. However, waking up in the connected state with a periodicity similar to that of the unconnected state leads to power wastage when the medical implant transceiver has to search for signals that typically have low strength. As the time for which the medical implant transceiver has to listen to the channel increases for signals with low strength, more power is wasted.
Communications between a controller (or “hub”) and an implant (or “node”) are subject to stringent regulatory restrictions. In particular, the hub often has to switch to a new operating channel selected from the ten channels total in the MICS band. The implant or node then needs to discover that new operating channel to communicate with the hub. A node cannot normally initiate a transmission to the hub, unless in an “implant event” (i.e., emergency). Furthermore, the node cannot choose the operating channel to use in an emergency, but instead the node must discover the hub's current operating channel to report the emergency. These are very challenging situations that typically are not encountered in wireless communications.
Existing solutions are either not power efficient or not in compliance with the FCC requirements for the MICS band. There is a need for a new technique for supporting communication between implants and controllers.